add {max_exn,min_exn}

src/Sequence.ml

@@ -554,6 +554,10 @@ let max ?(lt=fun x y -> x < y) seq =
       | Some y -> if lt y x then ret := Some x);
   !ret
 
+let max_exn ?lt seq = match max ?lt seq with
+  | Some x -> x
+  | None -> raise Not_found
+
 let min ?(lt=fun x y -> x < y) seq =
   let ret = ref None in
   seq
@@ -562,6 +566,15 @@ let min ?(lt=fun x y -> x < y) seq =
       | Some y -> if lt x y then ret := Some x);
   !ret
 
+let min_exn ?lt seq = match min ?lt seq with
+  | Some x -> x
+  | None -> raise Not_found
+
+(*$= & ~printer:string_of_int
+  100 (0 -- 100 |> max_exn ?lt:None)
+  0 (0 -- 100 |> min_exn ?lt:None)
+*)
+
 exception ExitHead
 
 let head seq =

src/Sequence.mli

@@ -290,10 +290,20 @@ val max : ?lt:('a -> 'a -> bool) -> 'a t -> 'a option
     @return None if the sequence is empty, Some [m] where [m] is the maximal
     element otherwise *)
 
+val max_exn : ?lt:('a -> 'a -> bool) -> 'a t -> 'a
+(** Unsafe version of {!max}
+    @raise Not_found if the sequence is empty
+    @since NEXT_RELEASE *)
+
 val min : ?lt:('a -> 'a -> bool) -> 'a t -> 'a option
 (** Min element of the sequence, using the given comparison function.
     see {!max} for more details. *)
 
+val min_exn : ?lt:('a -> 'a -> bool) -> 'a t -> 'a
+(** Unsafe version of {!min}
+    @raise Not_found if the sequence is empty
+    @since NEXT_RELEASE *)
+
 val head : 'a t -> 'a option
 (** First element, if any, otherwise [None]
     @since 0.5.1 *)